Update: I solved it by setting
.setGroupAlertBehavior(GROUP_ALERT_SUMMARY)
I am creating notifications like
new NotificationCompat.Builder(context, channel_id)
.setColor(..)
.setContentTitle(..)
.setSubText(..)
.setSmallIcon(..)
.setAutoCancel(true)
.setGroup(groupKey)
.setGroupSummary(true)
.setContentIntent(resultPendingIntent)
.build();
On 8.0 some devices are seeing double notification sound for every notification. There is a blog post around this
Some apps seem to have figured out a way to solve the issue? Help!